Electrical power generation, transmission and distribution relies on a number of transmission and distribution networks to transfer electrical power to a series of end users, as well as the generating equipment itself. Generating equipment includes the devices for generating the electrical power, most often an electrical machine such as for example a synchronous generator. An electrical power generation, transmission and distribution network also includes the devices necessary for actually bringing the power to the transmission or distribution networks, such as power transformers, instrument transformers, circuit breakers of various kinds, surge arresters etc., as well as secondary devices such as transducers, sensors and other devices needed for controlling the system. A transmission network can include high voltage lines or cables, both AC and DC, and a diversity of equipment meant to ensure the secure and reliable transmission of power, for example reactors, capacitors, Synchronous Condensers, Static Var Compensators, FACTS components, etc., and secondary devices as referred to above.
The background of this invention is of substations in electrical power transmission and distribution networks. The invention also relates to generation and distribution functions of plants including smaller and less traditional generation means such as micro turbines, wind farms, Combined Heat and Power plants (CHP) and other often privately owned generators that supply power to the network in a distributed fashion.
By tradition, and under conditions of a regulated market with state or community owned monopolies, a utility company is a company that operates and usually owns generating and/or transmission/distribution equipment. The utility company carries out a range of functions including operation, maintenance and extension of a network in accord with both present and future requirements.
HV electrical stations with equipment to operate, control, regulate and protect substations are well known. They have been provided by means of a large number or more or less dedicated hardware units, each one specially constructed to carry out a small number of functions in each area of application. Occasionally certain single functions have been included and somewhat standardised in computer software. Each of the necessary input signals have been specifically distributed, for example in a hard-wired arrangement, to the specific hardware units that require them. This way to achieve traditional operation, monitoring, control and protection of substations has demanded a large quantity of physical electrical connections between the different measuring, relay and control, regulation or protection etc. units. Thereby a large number of terminals and extensive cabling which has a direct relation to reliability of such prior art systems.
FIG. 1 shows a traditional realization of Control and Protection for a substation, in which every measuring signal, status signal, maneuvering signal, and so on, has its own interface unit, and a dedicated wire, or dedicated channel in a serial bus, to transfer the signal to or from the control equipment. It can be seen that a measuring signal to Control and Protection Unit Prot A of Id1 has it's own line through it's own I/O unit from DC current measuring signal 1 from the Process in a high voltage electrical substation. Likewise for Id2 which has it's own measuring equipment, own line to own I/O unit, and own line to Protection unit Prot B.
In the Control Equipment, every signal is handled by a dedicated unit for protection, or firing control etc. If more than one unit needs the same measuring signal, for example DC current, it is most probable that a new, separate measuring chain from the main circuit measuring unit, through the interface and the wire or connection, must be established for each unit needing the same signal. Sometimes the same signal can be used by more than one unit, provided the units are not physically located too far from each other, but in most cases this is not possible.
The principal drawback of this traditional method is that an                extensive set of measuring devices,        extensive set of dedicated interface units,        extensive wiring between interface and control equipment, and an        extensive set of dedicated units for performing all the control and protection functionsare all required. In addition, this solution is not very flexible, since practically every change in, or addition of, a control, regulation, monitoring or protection function requires installation of new hardware units at a measuring point and/or wiring to provide a new, for example, measuring device, and a new separate measuring chain between the measuring device and a control center.        
In more recent times information between certain hardware units has begun to be communicated using serial data connections, for example by means of fieldbuses. Connection of specific measurement signals to specific functional units, for example protection, has brought about a certain reduction in the quantity of terminal connections and cabling need for certain aspects of a substation control system.
Currently and under de-regulation market conditions have led to a re-focussing of priorities as regards the requirement for operation, maintenance and extension of a transmission and distribution network to better meet present requirements and future requirements. First, all these aspects are expected to be carried out under a more cost effective and predictable cost regime. Second, emphasis on meeting stringent power levels, power availability and power quality requirements set by regulatory authorities exists together with a generally much reduced willingness to invest in installed plant throughout the industry. Third, the growing numbers of small generators such as wind farms, micro turbines, and CHP plants being connected to power grids in recent times has made it more difficult to carry out network control functions such as balancing loads in parts of the network. Thus, utilities and operators are faced with the challenge of delivering high quality, reliable electric power at competitive rates to their customers by using limited manpower and resources. The inventor has determined that there is a need for devices, systems and methods that can provide operation, maintenance and extension of a substation in a power system in a cost-effective and reliable way.